enzymes notes

hydrolases function

hydrolysis

example enzyme that is a hydrolase

lipase

isomerases function

rearrange geometric or optical isomers (phosphoglucoisomerase) (isomerisation)

isomerisation

rearrangement of atoms

ligase/polymerase enzymes function

joint 2 or more chemicals together (acetyl co a synthase)

lyase enzyme functions

split compounds by cleaving c-c, c-s and some c-n bonds (fructose 1,6 diphosphate aldolase)

oxioreducatse enzyme function

catalyse oxidation and reduction reactions (transfer h+ from one molecule to another) (lactate dehydrogenase)

transferase

catalyse transfer of C-, N- or P- groups (hexokinase)

5 things enzymes act as

catalysts / activators / switches / inhibitors / effectors

how do enzymes lower activation energy

provide alternative reaction pathway with a lower activation energy (so more molecules have sufficient energy for active collisions to occur to convert substrates to products - affect rate at which equilibrium reached but do not affect equilibrium)

4 factors effect how effective an enzyme is

substrate concentration / temperature / ph / enzyme concentration

enzyme assays

chemical methods used to measure enzyme activity

2 types assay

continuous / discontinuous

continuous assay

monitored constantly in real time and rate determined by graphing product formation over time

discontinuous assay

rate of reaction measured at intervals / reaction is stopped and product formation is measured before restarting reaction

competitive inhibition

both enzyme and inhibitor are competing for same active site

does competitive inhibition affect maximum response

no

how overcome competitive inhibition

increase substrate concentration

effect of competitive inhibition on Km

increase

does a competitive inhibitor alter vmax?

no

effect of competitive inhibition on axis intercepts

changes x axis / doesn't change y axis

uncompetitive inhibition

inhibitor binds allosterically and causes a change in the overall structure of the enzyme leading to a decrease in catalytic activity

can you overcome uncompetitive inhibition by increasing substrate concentration

no

effect of uncompetitive inhibition on Vmax

decrease

effect uncompetitive inhibition ox axis intercepted

change y intercept / no change x intercept

irreversible inhibition

binds tightly to active site permanently inactivating the enzyme

1st order reaction

rate is proportional to concentration of a

2nd order reaction

rate is proportional to concentration of a^2

0 order reaction

rate does not vary with a

2 types of covalent modification

phosphorylation / methylation

cooperativity

when substrate binding affects substrate affinity

negative cooperativity

when substrate binding lowers the affinity for subsequent substrates

positive cooperativity

substrate binding increases the affinity for subsequent substrates

enzyme kinetics

mathematically monitoring the rate of enzyme activity

equation used to define enzyme kinetics

Michaelis menten equation

is there a greater quantity of substrate or enzyme in an enzyme substrate reaction

substrate

V0 equation

Vmax[s]/Km + [s]

Vo is

initial rate velocity

Vmax means

maximum velocity

Km means

Michaelis constant